With its launch of Pulse in 2007, Plaxo expanded into the social networking space, going beyond the address book to aggregate information feeds, like Flickr photos and calendars. Though the results were mixed (if not poor), its core business was attractive enough to draw the attention of Comcast, which acquired Plaxo for $150 million the following year. Since then, the company has tried to distance itself from its somewhat controversial past.

Last year, long-time CEO Ben Golub stepped down and was replaced by Justin Miller, who had been acting as GM. Under Miller’s direction, Plaxo became increasingly focused on working its way back to what gave birth to the company in the first place: trying to solve the problem of “address book decay”, a fancy way of saying “keeping your address book up to date”.

Recognizing how many of us struggle to keep our contacts up to date, Plaxo began devising products that would enhance its service, like a “smart search” tool that would act like an executive assistant using algorithms to comb the web and the Plaxo database around the clock to keep your directory up to date.

Today, Plaxo unveils what it has spent the last year building: a new family of address book-related services and what it hopes will be its golden goose, the Plaxo Personal Assistant, a service that intelligently makes automatic updates to your address book so that your contact information is always relevant. This announcement marks a significant relaunch for Plaxo, in which the company will begin to officially segue out of social networking and return to those address book roots.

Now, if you’re like me, you have several partial address books that you keep in a number of social networks, Web-based email accounts and on multiple mobile devices and hard drives, and you find keeping them up to date and secure to be a huge pain in the ass. The Plaxo Personal Assistant is designed to address this fragmentation by ensuring that your address book remains up to date in near realtime, so you have current information when you need it.

To accomplish this, Plaxo has forged partnerships with public profile databases, like ZoomInfo, to allow its software to crawl the swaths of public data available in these hubs. It compares your address book information with the database profiles and, if it finds information that it thinks is more current, it sends you a recommendation that you can approve or reject.

When you begin using the service, Plaxo will automatically alert you every time it finds more current data and seek your approval. However, the software is built to learn as it goes, so that, ostensibly, after accumulating enough data over a period of time, it will be able to auto approve — though the settings will allow you to choose. And, as the assistant may find multiple updates at one time, the service has a built-in interface that enables bulk approval.

As to the extent of Plaxo’s partnerships with public databases, CEO Justin Miller told me that the company is currently negotiating contracts with several other databases akin to ZoomInfo but was unable to share specifics for legal reasons.

As Plaxo is using scripts to crawl public data and compare it with your private info, security is an obvious concern. Miller assured me that Plaxo’s primary concern is keeping the 600 million unique contacts in Plaxo’s cloud private. During the process of vetting potential database partners, he said, the company was forced to reject several companies because they did not meet Plaxo’s security standards. Obviously, in light of Plaxo’s checkered history with spamming and data scraping, this is very reassuring.

In terms of pricing, Plaxo Personal Assistant is a paid service that will cost $79.99 a year — the equivalent of $6.67 a month. The Personal Assistant will be the premium subscription service in a set of address book management services, and Plaxo will continue to offer free services, like “Plaxo Basic”. Just as before, Basic will allow you to unify your contact information, access it from anywhere, at any time, yet, beginning today, the service will include the Plaxo “De-Duper”, a tool that scans your data for (and eliminates) duplicates.

The company also now offers apps for iPhone, iPad, BlackBerry, and Windows Mobile. Miller said that a Plaxo Android app is on the way.

Plaxo will continue to offer its “Platinum Sync” service, which allows two-way, realtime synchronization of your address book across your various devices and hardware, providing a consistent, updated address book from wherever you access it. And Platinum Sync and the Personal Assistant can be purchased together at a discounted price.

In his “State of Social Networking” post in December, VC Mark Suster described Plaxo as an old guard and past-its-prime company that “never quite figured out what to do with us all once we were connected online”. This impression of Plaxo is not uncommon. And seeing as other digital address books and tools, like Gist, Xobni, and Network Hippo, are trying to gain traction and market share, Plaxo’s relaunch today is designed to shake its reputation as a social network — and to establish it as the definitive resource for our contact info.

Considering that the company told me it has added 380,000 new users with address books in the last year, it has some momentum going into relaunch.

“We’re trying to put forth a new perception in peoples’ minds”, Plaxo GM Preston Smalley told me, “because otherwise they tend to fall back on old impressions”. At SxSW, Miller added, there are “a lot of sexy apps being launched”, but Plaxo’s relaunch and suite of new products aren’t intended to be flashy, nor focused on attracting page views, but on being seen as a utility for busy professionals. “Getting rid of Plaxo’s social networking”, Miller continued, is essential to getting back to the company’s bread and butter — keeping your address book updated, synced, and secured.